FAA Commercial Pilot Airplane (CAX)WeatherEasy
Which atmospheric condition is most conducive to the formation of advection fog?
- AWarm, moist air moving over a cold surface
- BCold, dry air moving over a warm surface
- CMoist air rising up a mountain slope
- DClear, calm night with high humidity
Show answer & explanationAnswer & explanation
Correct answer: A. Warm, moist air moving over a cold surface
Advection fog forms when warm, moist air moves horizontally over a cooler surface. As the warm, moist air is cooled from below to its dew point, condensation occurs, forming fog.
Why the other options are wrong
- B. This condition would more likely lead to clear skies or perhaps steam fog if the water is much warmer.
- C. This describes upslope fog, where air is cooled adiabatically as it rises.
- D. This describes radiation fog, which forms on still, clear nights as the ground cools by radiation.
Advection Fog
Fog formed when warm, moist air moves horizontally over a cooler surface, cooling to its dew point.
- Requires horizontal air movement (advection).
- Common in coastal areas where warm air moves over cold ocean currents.
- Can be widespread and persistent.
Memory trick: Advection's a wave of warm air, over cool ground, fog's everywhere.